Research On Key Technology Of Variable Stiffness Actuator For Service Robot

With the evolution of robotics, the applications of the robot gradually expand fromindustrial to social services. Simultaneously, the work environment of the robot is no longerfixed, but is full of change and unknown condition. Entering into the social servicesapplication, there are extremely frequent human-robot interaction when the robot work withpeople or the surrounding environment, which result in higher requirements of safety,environmental suitability and energy efficiency for robot. Joint actuator is one of the keycomponents of the robot, and its property determine the integrated performance of the robot.Only considering the mechanical structure of joint actuator, a variable stiffness joint actuatorwhich was based on an elastic element was proposed in this dissertation, and its propertieswere researched. The specific work was organized as follows:(1) The researching background and significance of variable stiffness actuator wasdescribed. The concept, components, classification and basic principles of varying stiffnessactuator were briefly introduced. The present studies and the direction of the investigation ofvariable stiffness were summarized.(2) According to the principle of structure-controlled stiffness, four elastic elements weredesigned. The design ideas and methods of the elastic element were introduced in detail, andthe design matrix was established. The configuration of the elastic element were establishedby using topology optimization technique, and their advantages and disadvantages weresummarized. At the same time, the parameters which had an influence on the stiffnesscharacteristics of the elastic element were analyzed. Based on the elastic element, three typesof variable stiffness actuator have been designed, and their characteristics and work principleswere simply elaborated.(3) Under the structural characteristics of the elastic element, the stiffness characteristicsof the elastic elements were analyzed by using analytical method or finite element simulation(FEM) method respectively, and their moment-displacement curve and stiffness characteristiccurve were got and elaborated. The strength and instability of the elastic elements wereanalyzed by using FEM method.(4) The physical model of variable stiffness actuator was built. On the basis of the model,the dynamic model of the system was obtained. By analyzing Nyquist curve and the Bodediagram of open-loop system, it can lead to the conclusion that the system was stable. Theresponse characteristic of the system was analyzed by using the Simulink module of MATLAB.(5) The collision model of the actuator was constructed, and the definition and thestandard of safety were given. The difference between the traditional actuator and variablestiffness actuator in energy output was made by using method of comparative analysis. Withthe collision and the tossing tests, the actuator’s capability of absorbing the shock of impactand energy storage was testified. A prototype of variable stiffness actuator has been developedfor the later experimental study.